The number of echoes combined into a single image or image set in multiple echo imaging sequences or echo-train techniques such as rapid acquisition with relaxation enhancement (RARE), fast-spin echo (FSE), and turbo spin-echo (TSE). In RARE imaging, the ETL typically equals the acceleration factor.
As for tooth pain, it is caused by a reaction of the nerves inside a tooth's pulp chamber with the severity dependent upon the type and degree of the stimulus. What follows are some examples of symptoms you may be feeling and their possible causes.
5. Why is it difficult to identify which tooth which is causing the pain? The trigeminal nerve is the great nerve of the face and jaws. All the teeth are linked by branches of the same nerve. A pain may be felt in the upper jaw, when the cause is a tooth in the lower jaw. This is called a 'referred pain'. It occurs when decay within a tooth is the source of the pain. When pain is caused by decay that has spread to the area around a tooth, it is quite simple to locate it.